linux-kernel - Re: [PATCH 1/8] clk: Add clk_bulk

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Message-ID: <b67b5043-f5e5-826a-f0b8-f7cf722c61e6@arm.com>
Date:   Mon, 19 Feb 2018 16:29:12 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Maciej Purski <m.purski@...sung.com>, linux-media@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org
Cc:     David Airlie <airlied@...ux.ie>,
        Michael Turquette <mturquette@...libre.com>,
        Kamil Debski <kamil@...as.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Thibault Saunier <thibault.saunier@....samsung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Russell King <linux@...linux.org.uk>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Hoegeun Kwon <hoegeun.kwon@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Inki Dae <inki.dae@...sung.com>,
        Jeongtae Park <jtp.park@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Hans Verkuil <hansverk@...co.com>,
        Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH 1/8] clk: Add clk_bulk_alloc functions

Hi Maciej,

On 19/02/18 15:43, Maciej Purski wrote:
> When a driver is going to use clk_bulk_get() function, it has to
> initialize an array of clk_bulk_data, by filling its id fields.
> 
> Add a new function to the core, which dynamically allocates
> clk_bulk_data array and fills its id fields. Add clk_bulk_free()
> function, which frees the array allocated by clk_bulk_alloc() function.
> Add a managed version of clk_bulk_alloc().

Seeing how every subsequent patch ends up with the roughly this same stanza:

	x = devm_clk_bulk_alloc(dev, num, names);
	if (IS_ERR(x)
		return PTR_ERR(x);
	ret = devm_clk_bulk_get(dev, x, num);

I wonder if it might be better to simply implement:

	int devm_clk_bulk_alloc_get(dev, &x, num, names)

that does the whole lot in one go, and let drivers that want to do more 
fiddly things continue to open-code the allocation.

But perhaps that's an abstraction too far... I'm not all that familiar 
with the lie of the land here.

> Signed-off-by: Maciej Purski <m.purski@...sung.com>
> ---
>   drivers/clk/clk-bulk.c   | 16 ++++++++++++
>   drivers/clk/clk-devres.c | 37 +++++++++++++++++++++++++---
>   include/linux/clk.h      | 64 ++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 113 insertions(+), 4 deletions(-)
> 

[...]
> @@ -598,6 +645,23 @@ struct clk *clk_get_sys(const char *dev_id, const char *con_id);
>   
>   #else /* !CONFIG_HAVE_CLK */
>   
> +static inline struct clk_bulk_data *clk_bulk_alloc(int num_clks,
> +						   const char **clk_ids)
> +{
> +	return NULL;

Either way, is it intentional not returning an ERR_PTR() value in this 
case? Since NULL will pass an IS_ERR() check, it seems a bit fragile for 
an allocation call to apparently succeed when the whole API is 
configured out (and I believe introducing new uses of IS_ERR_OR_NULL() 
is in general strongly discouraged.)

Robin.

> +}
> +
> +static inline struct clk_bulk_data *devm_clk_bulk_alloc(struct device *dev,
> +							int num_clks,
> +							const char **clk_ids)
> +{
> +	return NULL;
> +}
> +
> +static inline void clk_bulk_free(struct clk_bulk_data *clks)
> +{
> +}
> +
>   static inline struct clk *clk_get(struct device *dev, const char *id)
>   {
>   	return NULL;
>